Non-contact bias charge roll biased with burst modulation waveform
View Patent ↗A method of operating an electrostatographic printing apparatus, the apparatus including a charge-retentive member defining an imaging surface and a charging device for placing a charge on the imaging surface, a gap existing between the imaging surface and the charging device, including applying an electrical bias to the charge-retentive member by generating a burst modulated waveform.
1. A method of operating an electrostatographic printing apparatus, comprising:
applying an electrical bias to a charge-retentive member of the electrostatographic printing apparatus, said charge-retentive member defining an image surface, the electrostatographic printing apparatus further including a charging device for placing a charge on the imaging surface, a gap existing between the imaging surface and the charging device, said applying including generating a burst modulated waveform,
wherein the generating includes employing a DC offset superimposed on an AC waveform,
and the applying includes generating a first AC waveform carrier frequency over a time t 1 during which the AC waveform is gated on and a second AC waveform burst frequency over a time t 2 during which the AC waveform is gated on and off,
wherein the average AC current over time t 2 is less than the AC current over time t 1 .
2. The method of claim 1 , wherein the generating includes fixing a burst rate to constant frequency and varying a carrier frequency.
3. The method of claim 1 , wherein the generating includes fixing a carrier frequency to constant frequency and varying a burst rate.
4. The method of claim 1 , wherein the generating includes modifying a waveform selected from the group consisting of sinusoidal, rectangular, and triangular.
5. The method of claim 2 , wherein the generating includes employing a carrier frequency between 500 and 5000 Hertz.
6. The method of claim 1 , wherein the generating includes employing a burst rate between 250 and 4000 Hertz.
7. The method of claim 1 , wherein the generating includes employing a AC voltage between 1000 Vpp and 3000 Vpp.
8. The method of claim 1 , wherein the generating includes employing a duty cycle between 10% and 99%.
9. A method of charging a charge-retentive member of an electrostatographic printing apparatus, comprising:
applying an electrical bias from a charging member of the electrostatographic printing apparatus to an imaging surface of the charge-retentive member, a gap existing between the imaging surface and the charging device, said applying including generating a burst modulated waveform,
wherein the generating includes employing a DC offset superimposed on an AC waveform,
and the applying includes generating a first AC waveform carrier frequency over a time t 1 during which the AC waveform is gated on and a second AC waveform burst frequency over a time t 2 during which the AC waveform is gated on and off,
wherein the average AC current over time t 2 is less than the AC current over time t 1 .
10. The method of claim 9 , wherein the generating includes fixing a burst rate to constant frequency and varying a carrier frequency.
11. The method of claim 9 , wherein the generating includes fixing a carrier frequency to constant frequency and varying a burst rate.
12. The method of claim 9 , wherein the generating includes modifying a waveform selected from the group consisting of sinusoidal, rectangular, and triangular.
13. The method of claim 10 , wherein the generating includes employing a carrier frequency between 500 and 5000 Hertz.
14. The method of claim 9 , wherein the generating includes employing a burst rate between 250 and 4000 Hertz.
15. The method of claim 9 , wherein the generating includes employing a AC voltage between 1000 Vpp and 3000 Vpp.
16. The method of claim 9 , wherein the generating includes employing a duty cycle between 10% and 99%.